How severe is CVE-2025-40939?

CVE-2025-40939 has a CVSS 3.x base score of 4.6, rated medium severity. It is exploitable over physical access with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2025-40939 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (8th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-40939?

CVE-2025-40939 affects Siemens Simatic Cn 4100 Firmware. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-40939?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-40939 have an EU (EUVD) identifier?

Yes. CVE-2025-40939 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-201917.

When was CVE-2025-40939 published?

CVE-2025-40939 was published on 2025-12-09 and last updated on 2026-06-17.

CVE-2025-40939

CVE-2025-40939 is a medium-severity vulnerability in Siemens Simatic Cn 4100 Firmware with a CVSS 3.x base score of 4.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-284.

Key facts

Severity: Medium (CVSS 3.x base score 4.6)
CVSS v4: 5.1
EPSS exploit prediction: 0% (8th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-201917
Weakness: CWE-284
Affected product: Siemens Simatic Cn 4100 Firmware
Published: 2025-12-09
Last modified: 2026-06-17

Description

A vulnerability has been identified in SIMATIC CN 4100 (All versions < V4.0.1). The affected device contains a USB port which allows unauthenticated connections. This could allow an attacker with physical access to the device to trigger reboot that could cause denial of service condition.

Frequently asked questions

What is CVE-2025-40939?: A vulnerability has been identified in SIMATIC CN 4100 (All versions < V4.0.1). The affected device contains a USB port which allows unauthenticated connections. This could allow an attacker with physical access to the device to trigger reboot that could cause denial of service condition.
How severe is CVE-2025-40939?: CVE-2025-40939 has a CVSS 3.x base score of 4.6, rated medium severity. It is exploitable over physical access with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2025-40939 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (8th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-40939?: CVE-2025-40939 affects Siemens Simatic Cn 4100 Firmware. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-40939?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-40939 have an EU (EUVD) identifier?: Yes. CVE-2025-40939 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-201917.
When was CVE-2025-40939 published?: CVE-2025-40939 was published on 2025-12-09 and last updated on 2026-06-17.

References

https://cert-portal.siemens.com/productcert/html/ssa-416652.html

Affected products (1)

cpe:2.3:o:siemens:simatic_cn_4100_firmware:*:*:*:*:*:*:*:*

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